Page Authority Explained: How Moz Calculates PA, What It Means, and How to Improve It
Page authority is a score from 1 to 100 developed by Moz that predicts how likely a specific webpage is to rank in Google search results. It is calculated using a machine-learning model that analyses dozens of link-based signals — primarily the quantity and quality of backlinks pointing at that page — and compresses them into a single logarithmic score. In short, the higher a page’s page authority score, the stronger its predicted ranking power.
Understanding page authority is essential for SEO professionals who benchmark link equity, compare competitor pages, and prioritise link-building campaigns. Furthermore, knowing exactly how the metric works — and what it cannot tell you — helps you avoid common misinterpretations that lead to wasted effort.
★ Key Takeaways
- →Page authority is scored on a logarithmic 1–100 scale using Moz’s machine-learning model. For a deeper walkthrough, see our Moz Keyword Difficulty Checker: Full Guide (2025).
- →The primary inputs are the quantity and quality of external backlinks pointing to a page.
- →PA is a relative metric — it shifts as Moz’s entire web index changes over time.
- →PA correlates with ranking ability but is not a direct Google ranking factor.
- →Domain Authority (DA) measures an entire domain; page authority measures a single URL.
- →On-page SEO does not directly influence PA — only link signals do.
What Is Page Authority? A Clear Definition
Page authority (PA) is a proprietary SEO metric developed by Moz. Specifically, it predicts the likelihood that a single webpage will rank well in search engine results pages (SERPs). The score ranges from 1 (least authoritative) to 100 (most authoritative), and it is calculated using a machine-learning algorithm trained against real Google ranking data.
Importantly, page authority is a predictive metric — not a prescriptive one. In other words, it does not tell Google how to rank your page. Instead, it reflects the link equity a page has accumulated and uses that data to estimate competitive ranking potential.
For example, a blog post that earns hundreds of high-quality backlinks from respected publications will have a high PA score. Consequently, Moz’s model predicts that post is more likely to outrank a competing page with fewer or lower-quality links.
Page Authority vs. Domain Authority: Why the Distinction Matters
Moz produces two closely related authority metrics. Therefore, understanding which to use — and when — is critical for accurate SEO analysis. Domain Authority (DA) measures the overall strength of an entire root domain. Page authority, in contrast, evaluates one specific URL in isolation.
How Moz Calculates Page Authority: The Core Formula
Moz does not publish a literal mathematical formula for page authority. Instead, it trains a machine-learning algorithm against real Google search result data. Specifically, the model is fed a wide array of link metrics collected from Moz’s own crawl index — and the output is a single score that best correlates with actual Google rankings.
The most heavily weighted inputs include the following signals:
Key Signals That Drive Page Authority Scores
- Linking Root Domains: The number of unique domains pointing to a page. More authoritative unique domains means a higher page authority score. Furthermore, diversity of linking domains matters more than sheer volume from a single source.
- Total External Links: The raw count of inbound links. However, uniqueness is weighted more heavily than raw volume — 10 links from 10 different domains outweigh 10 links from one domain.
- MozRank: A link popularity score that reflects both the quantity and quality of links pointing at a page. It is modelled on a flow-of-authority concept similar to Google’s original PageRank algorithm.
- MozTrust: Measures how close a page is to trusted “seed” sites — for example, government (.gov) and education (.edu) domains. Pages that earn links from these high-trust sources receive a MozTrust benefit.
- Link Profile Quality: The page authority of the pages that link to your target page. Consequently, a single link from a PA 80 page contributes far more equity than dozens of links from PA 15 pages.
- Spam Score Influence: While not a direct PA input, links from high-spam-score domains reduce the overall trust of a link profile, which in turn suppresses PA. Therefore, a clean link profile is essential.
All of these signals are combined through the ML model to produce the final 1–100 score. Moz periodically retrains the model against fresh Google SERP data. As a result, PA scores can fluctuate even when no changes have been made to a page or its link profile.
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Page authority is best used as a comparative tool — not an absolute grade. Two points of PA difference at the top of the scale can represent millions of links of difference in the underlying data.
— Moz, Page Authority Documentation
The Logarithmic Scale: Why Page Authority Gets Harder to Improve
The 1–100 range is logarithmic, not linear. This is one of the most important practical details about how Moz calculates page authority. On a linear scale, moving from 10 to 20 requires the same effort as moving from 50 to 60. On a logarithmic scale, however, moving from 50 to 60 requires exponentially more link equity than moving from 10 to 20.
What the Logarithmic Scale Means in Practice
- A brand-new page with zero backlinks starts at PA 1.
- Earning a handful of quality links can quickly push a page to PA 20–30.
- Reaching PA 50+ requires a substantial, high-quality inbound link profile built over time.
- Pages above PA 70 are typically major publications, Wikipedia articles, or heavily linked cornerstone content.
- Pages above PA 80 represent truly elite authority — think the New York Times homepage or major government portals.
Because of this logarithmic compression, absolute PA numbers matter far less than relative comparisons. For example, a page with PA 45 competing against PA 40 pages is well-positioned. In contrast, the same PA 45 page competing against PA 65 pages faces a steep uphill battle regardless of its content quality.
Similarly, this explains why it is nearly impossible to reach a PA of 100. The scale is calibrated so that the world’s most authoritative pages — the top Wikipedia articles, the highest-authority government resources — occupy the very top of the range. In practice, most well-optimised content pages land between PA 30 and PA 55.
Page Authority Score Benchmarks at a Glance
Why Page Authority Scores Fluctuate (Even Without Doing Anything)
One of the most common points of confusion is that a page’s PA score can drop even when no links have been lost and no on-page changes have been made. This happens for two key reasons — and understanding both will save you from unnecessary panic during routine score updates.
Reason 1
Relative Scoring Across the Index
PA is calculated relative to every other page in Moz’s index. If the web grows and millions of new high-authority pages are added, your PA can decrease — even though your own link profile hasn’t changed at all. In other words, you are always being ranked against the entire web.
Reason 2
Periodic ML Model Retraining
Moz periodically retrains its machine-learning model against fresh Google SERP data. When the model is updated to better reflect current Google behaviour, all PA scores are recalibrated simultaneously. As a result, even sites with growing link profiles can see temporary dips during retraining events.
This is why Moz explicitly advises tracking PA trends over time and comparing pages within the same competitive set — rather than treating any single PA number as a fixed, immutable grade.
How Often Does Moz Update Page Authority?
Moz updates PA scores approximately every 3–4 weeks as its web crawler re-indexes links and the underlying data refreshes. Major model retraining events occur less frequently — however, when they do occur, they can cause larger, site-wide score shifts across the entire Moz index simultaneously.
Therefore, if you notice a sudden, unexplained drop in PA across your entire site, a model retraining event — rather than a link loss — is the most likely explanation. In contrast, a drop on only one or two pages typically signals an actual change in that page’s link profile.
How to Check Your Page Authority Score for Free
Before working to improve page authority, you need a reliable way to measure it. Fortunately, Moz provides several free and paid tools for checking PA scores.
- Moz Link Explorer: The primary tool for checking page authority. Free accounts receive a limited number of daily queries. Paid Moz Pro subscribers get unlimited access plus bulk PA checking for large-scale analysis.
- MozBar Browser Extension: A free Chrome extension that overlays PA and DA scores directly on SERPs and any webpage you visit. It is particularly useful for on-the-fly competitor analysis.
- Moz’s Free Domain Analysis Tool: Provides a quick PA and DA snapshot for any URL. However, it is limited to one lookup per day without a free account.
- Third-Party SEO Tools: Platforms such as SEMrush and Ahrefs display their own authority metrics (Authority Score and URL Rating, respectively), which are conceptually similar to page authority but use different underlying data and methodologies.
Specifically, for professional-level competitive analysis, Moz Pro’s bulk PA checker allows you to pull scores for hundreds of URLs simultaneously — an essential capability when auditing large content libraries or entire competitor domains.
How to Improve Page Authority: 7 Proven Strategies
Because page authority is driven almost entirely by link-based signals, the strategies to improve it are rooted in link acquisition and link equity optimisation. Below are the most effective methods, ordered from highest to lowest impact.
Earn High-Quality Backlinks from Authoritative Pages
A single editorial link from a PA 70+ page can move your score more than 50 links from PA 20 pages. Therefore, prioritise earning placements on respected publications, industry databases, and news sites in your niche. Guest posts, expert commentary (HARO/Connectively), and digital PR campaigns are the most reliable paths to high-authority backlinks.
Build Smart Internal Links to Target Pages
Internal links pass link equity from your high-PA pages to the pages you want to boost. A well-structured internal linking strategy can meaningfully improve page authority for deep content pages that have limited external backlinks. Furthermore, contextual internal links — placed naturally within body copy — pass more equity than navigational links.
Audit and Remove Toxic Links
Spammy or low-quality inbound links dilute your link profile’s overall trust signals. Specifically, high Moz Spam Score links can drag down MozTrust and ultimately suppress page authority. Conduct regular link audits using Moz Link Explorer or Google Search Console — and disavow harmful links via Google’s Disavow Tool when necessary.
Create Linkable Asset Content
Original research, comprehensive guides, free tools, interactive calculators, and data-driven studies naturally attract backlinks at scale. The more a page is cited by others, the faster its page authority grows. In addition, linkable assets tend to compound over time — a well-cited resource page continues earning new links for months or years after publication.
Consolidate Link Equity via 301 Redirects
If you have duplicate or near-duplicate pages splitting link equity across multiple URLs, consolidate them with 301 redirects. This concentrates authority into a single canonical URL — and consequently boosts that page’s PA by eliminating the dilution effect of fragmented link profiles.
Reclaim Lost and Broken Backlinks
Links pointing to deleted or redirected pages leak equity. Use Moz Link Explorer to identify backlinks pointing to 404 error pages on your site — then reinstate the content or redirect the dead URL to a relevant live page. Similarly, reach out to sites linking to outdated or moved content and request a URL update.
Diversify Your Linking Root Domains
Moz’s algorithm rewards link diversity. In particular, links from a wide variety of root domains signal broader relevance and authority than many links from a single source. Therefore, prioritise acquiring links from new domains over getting additional links from domains that already link to your page.
What Is a Good Page Authority Score?
There is no universal “good” page authority score — it depends entirely on your competitive landscape. A PA of 35 may be dominant in a niche industry but thoroughly weak in a competitive vertical where the top-ranking pages carry PA 60+.
The correct approach is to always benchmark your PA against the pages you are actually competing with in the SERPs. Specifically, use MozBar or Link Explorer to check the PA of the top 5–10 results for your target keyword. If your target page has a PA within 5–10 points of those pages, you are competitive from a link authority standpoint.
However, remember that page authority is only one factor in rankings. Above all, Google evaluates relevance, content quality, E-E-A-T (Experience, Expertise, Authoritativeness, and Trustworthiness), and user engagement signals alongside link authority. Therefore, a page with slightly lower PA but significantly better content can still outrank a higher-PA competitor.
Page Authority vs. Other Authority Metrics
Moz’s page authority is the most widely known page-level authority metric, but it is not the only one. Understanding how it compares to alternatives helps you build a more complete picture:
- Moz Page Authority: Machine-learning model trained on Google SERP data. Scores 1–100 logarithmically. Updated every 3–4 weeks.
- Ahrefs URL Rating (UR): Measures the strength of a page’s backlink profile on a 0–100 logarithmic scale. Similar concept to PA but uses Ahrefs’ independent crawl data.
- SEMrush Authority Score: A composite score combining backlink data, organic search traffic, and spam factors. As a result, it blends link authority with actual traffic performance.
- Google’s Internal PageRank: Google’s original link authority algorithm. Not publicly disclosed — however, Google Search Console’s internal linking report offers a partial proxy for understanding how Google distributes equity across a site.
Frequently Asked Questions About Page Authority
Conclusion: Using Page Authority Effectively
Understanding page authority gives you a significant edge in competitive SEO. Specifically, it is a machine-learning score built from dozens of link-based signals — primarily the quantity, quality, and trustworthiness of inbound links — compressed into a logarithmic 1–100 scale that predicts ranking potential. However, page authority is a relative metric that shifts constantly with the broader web. Consequently, the smartest way to use it is as a competitive benchmarking tool, not a fixed target. Focus on earning authoritative backlinks from diverse linking root domains, building smart internal linking structures, reclaiming lost link equity, and creating genuinely cite-worthy content. Do those things consistently, and your page authority score will reflect the real authority your pages have built.
